Surface package type semiconductor package and method of producing semiconductor memory

ABSTRACT

In surface packaging of thin resin packages such as resin molded memory ICs or the like, cracks of the package occur frequently at a solder reflow step where thermal impact is applied to the package because the resin has absorbed moisture before packaging. To solve this problem, the devices are packaged moisture-tight at an assembly step of the resin molded devices where the resin is still dry, and are taken out from the bags immediately before the execution of surface packaging.

This application is a Divisional application of application Ser. No.09/843,937, filed Apr. 30, 2001, now U.S. Pat. No. 6,443,298 thecontents of which are incorporated herein by reference in theirentirety, which is a Continuation application of application Ser. No.09/387,049, filed Aug. 31, 1999, now U.S. Pat. No. 6,223,893, issued May1, 2001, which is a Continuation application of application Ser. No.09/094,490, filed Jun. 10, 1998, now U.S. Pat. No. 5,988,368 thecontents of which are incorporated herein by reference in theirentirety, which is a Continuation application of application Ser. No.08/712,559, filed Sep. 13, 1996, now U.S. Pat. No. 5,803,246, which is aContinuation application of application Ser. No. 08/264,745, filed Jun.23, 1994, now U.S. Pat. No. 5,607,059, which is a Continuationapplication of application Ser. No. 07/791,539, filed Nov. 14, 1991, nowabandoned, which is a Continuation application of application Ser. No.07/392,029, filed Aug. 10, 1989, now U.S. Pat. No. 5,095,626, which is aDivisional application of application Ser. No. 07/124,925, filed Nov.23, 1987, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a technique for preventing peel of a packageinterface and crack when a surface package type semiconductor package ismounted to a packaging substrate such as a printed circuit board.

In surface mount package type semiconductor packages such as a smalloutline package (SOP), a squad flat package (QFP), a plastic leaded chipcarrier (PLCC), and the like, the size and thickness of the packages aremore and more reduced in order to cope with the increase in the size ofa semiconductor chip stored in the package and package strength tends todecrease.

Therefore, it has become difficult to produce a thin resin molded IChaving high reliability.

Incidentally, mention can be made of “IC PACKAGING TECHNIQUE”, publishedby Kogyo Chosakai K. K., Jan. 15, 1980, pp. 135–156, as a prior artreference describing surface package type semiconductor packages.

Furthermore, as disclosed in Japanese Patent Laid-Open No. 178877/1986by Otsuka et al. (Aug. 11, 1986), a proposal has been made to put adesiccant into a magazine or to seal a conveying tray in a bag of avinyl sheet or the like.

SUMMARY OF THE INVENTION

When examining packaging reliability and strength of these thin typepackages, the inventors of the present invention have found out thatwhen heat is applied to the package when surface-mounting the package toa mounting substrate such as a printed circuit board such as at the timeof solder reflow, a moisture that has entered the package causes drasticvolume expansion and peel of the package interface and crack develops.

To cope with this problem, it has been customary to bake the package at125° C., for example, for a period as long as 16 to 24 hours beforesolder reflow, but this method is believed inefficient because a furnacefor baking must be prepared and particularly because baking must be madefor the long period.

As a result of examination of the origin of the moisture causing thecracking described above, the inventors of the invention have clarifiedthat the moisture in the air enters the package during the period fromtransfer molding of a chip component by a resin to solder reflow and islikely caused by dew.

Though the Otsuka et al. method described already provides aconsiderable effect, the problem cannot be solved completely by thismethod in view of the recent product situation where the thickness andsize of the packages are reduced more and more to store greater chipsand of the severe environment where the products are shipped byairplanes.

It is therefore an object of the present invention to provide atechnique which prevents interface peeling and cracking of a surfacemount package type package.

It is another object of the present invention to provide a highlyreliable high density packaging technique.

It is still another object of the present invention to provide anefficient solder reflow technique.

It is still another object of the present invention to provide aneffective shipment method of electronic components.

It is a further object of the present invention to provide an effectivepreservation method of semiconductor devices sealed by a thin resinpackage.

It is still another object of the present invention to provide highfreedom for the conditions of executing an assembly process.

It is still another object of the present invention to provide anassembly process which will be suitable for surface mount package.

It is still another object of the present invention to provide anefficient surface mount type packaging technique.

It is still another object of the present invention to improvemoisture-proofness of resin-molded ICs, or the like.

It is still another object of the present invention to provide apackaging technique of resin-molded ICs or the like which will besuitable for automatic packaging.

It is still another object of the present invention to provide apreservation method of ICs, components, electronic devices, and thelike, which have high moisture-proofness and do not require baking evenwhen stored for a long period.

It is still another object of the present invention to provide apackaging method of electronic components such as ICs which can easilydiscriminate the existence of pin-holes.

It is still another object of the present invention to provide amoisture-proofing package technique of ICs or the like which does notneed a large space requirement.

It is still another object of the present invention to provide amoisture-proofing packaging technique of ICs or the like which caneasily judge the degree of hygroscopicity of ICs or the like.

It is still another object of the present invention to provide amoisture-proofing bag having a display portion for displaying the degreeof hygroscopicity of ICs or the like.

It is still another object of the present invention to provide a packagemember for surface package type packages which can easily represent thedegree of hygroscopicity of ICs or the like.

It is still another object of the present invention to provide anefficient surface mounting method of resin-molded ICs or the like.

It is still another object of the present invention to provide anassembly process which will be suitable for resin-molded electroniccomponents storing therein integrated circuits having a large chip size.

It is still another object of the present invention to provide ashipment method of electronic devices such as resin-molded ICs whichwill be suitable for the shipment of the electronic devices by airplanes.

It is still another object of the present invention to provide amoisture-proofing packaging technique of resin-molded ICs or the likewhich does not undergo dewing even at low temperatures.

It is still another object of the present invention to provide atechnique which can confirm the state of hygroscopicity of amoisture-proofing package inside the package from the outside thereof.

These and other objects and novel features of the present invention willbecome more apparent from the following detailed description when takenin conjunction with the accompanying drawings.

Among the inventions disclosed herein, a typical example is as follows.

In the present invention, a surface mount package type package stored ina magazine is put into an interior box, the interior box is then placedinto a transparent resin bag using, as the base, a polyester havingmoisture permeability of up to 2.0/m²·24 hrs, for example, and having asurface intrinsic resistance of 10⁶ Ohms on the outside and up to 10¹¹Ohms on the inner side, and the open portion of the bag is heat-sealedafter removing the air. Furthermore, a desiccant such as silica gel isput into the interior box.

According to this arrangement described above, the surface mount packagetype package is stored in the interior box and the moisture-proofing bagoutside the box and sealed completely by deaeration and heat seal and isfree from the influences of external moisture. Therefore, the interfacepeel and crack of the package do not occur even after solder reflowwithout the need of the troublesome baking operation. Particularlybecause the polyester having moisture permeability of up to 2.0 g/m²·24hours is used as the base of the resin bag in the present invention,moisture-proofness is high and heat seal is possible so that the effectof checking intrusion of the external air is high. The surface intrinsicresistance of the bag is up to 10¹¹ ohms on its inner surface and up to10⁶ ohms on its outer surface in order to prevent any charge.Furthermore, silica gel is placed between the magazine and the wallsurface of the interior box in the present invention in order to absorbthe moisture so that the surface package type package is not muchaffected by the external moisture.

Still another example of the inventions disclosed herein is as follows.

Namely, the present invention provides a transparent moisture-proofingpackaging bag for moisture-proofing and packaging an electroniccomponent, which bag is equipped with a moisture indicator for detectingthe degree of hygroscopicity inside the moisture-proofing bag at aportion which is visible from outside.

According to the means described above, since the moisture indicator fordetecting the moisture inside the transparent moisture-proofing bag isdisposed at a position visible from outside, the degree ofhygroscopicity of the bag can be confirmed from outside the bag.

Still another typical example of the inventions disclosed hereinprovides a package which comprises a semiconductor chip on which atleast one electronic device is formed, a resin-molding member coveringat least a part of the main plane of the semiconductor chip, and amoisture-proofing bag comprising a multi-layered film containing atleast one metal sheet, for cutting off the resin-molding member fromoutside.

Still another typical example of the inventions disclosed hereinprovides a package of a number of (about 10) resin-molded semiconductordevices which are stored in a plastic magazine, whose outside portion issealed air-tight by a moisture-proofing film.

Still another typical example of the inventions disclosed hereinprovides an air-tight package made of a moisture-proofing film andincluding a number of resin-molded semiconductor devices, a plurality ofdevice storing magazines storing therein a line of resin-moldedsemiconductor devices, an interior box for aligning a plurality ofmagazines and storing them therein while they are in close contact withone another, a packaging bag made of a moisture-proofing sheet member,storing therein the interior box and sealed air-tight, and a desiccantplaced in the packaging bag.

Still another typical example of the inventions disclosed herein providean air-tight package for a number of surface mount package typeresin-molded semiconductor devices which comprises an exterior box madeof cardboard, a number (at least five to six) of packaging bags made ofa moisture-proofing film and sealed air-tight, a plurality of interiorboxes made of paper and stored in the packaging bag, a plurality oftube-like magazines for conveying semiconductor devices, stored in theinterior boxes, respectively, a number of surface package typeresin-molded semiconductor integrated circuit devices stored in themagazines, respectively, and a desiccant stored in each of the interiorboxes.

Still another typical example of the inventions disclosed hereinprovides an air-tight package for a large number of surface mountpackage type resin-molded semiconductor integrated circuit devices whichcomprises an exterior box made of cardboard, a plurality of packagingbags made of a moisture-proofing film and sealed air-tight inside theexterior box, at least one conveying auxiliary member for protecting anumber (at least five to six) of resin-molded semiconductor devicesstored in the packaging bags, a number of resin-molded semiconductorintegrated circuit devices stored in or on the auxiliary member, and adesiccant stored in each of the packaging boxes.

Still another typical example of the inventions disclosed hereinprovides an air-tight package for at least one resin-moldedsemiconductor device which comprises a packaging bag made of amoisture-proofing film, at least one conveying auxiliary member storedin the packaging bag, at least one resin-molded semiconductor devicestored in the packaging bag and stored in or on the auxiliary member,and a desiccant placed in the packaging bag.

Still another typical example of the inventions disclosed hereinprovides an air-tight package for at least one resin-moldedsemiconductor device which comprises a packaging bag made of amoisture-proofing film and sealed air-tight, at least one resin-moldedsemiconductor device stored in the packaging bag, and a desiccant placedin the packaging bag.

Still another typical example of the inventions disclosed hereinprovides an air-tight package for at least one resin-moldedsemiconductor device which comprises a packaging bag made of amoisture-proofing film and sealed air-tight, at least one resin-moldedsemiconductor device stored in the packaging bag, and a desiccant storedin the packaging bag or formed on the inner surface of the packagingbag.

Still another typical example of the inventions disclosed hereinprovides a package comprising a semiconductor chip on which at least oneelectronic device is formed, a moisture-proofing bag for cutting off thesemiconductor chip from outside, and humidity display means disposed inthe moisture-proofing bag and capable of being recognized from inside.

Still another typical example of the inventions disclosed hereinprovides a package comprising a tube-like magazine for storing a line ofa number (at least five to six) of resin-molded semiconductor devices, anumber of resin-molded semiconductor devices stored in the magazine, andhumidity display means disposed in the magazine in such a manner as tobe visible from outside.

Still another typical example of the inventions disclosed hereinprovides a package for a large number (at least ten) of resin-moldedsemiconductor devices, sealed air-tight by a moisture-proofing film,said package being equipped thereinside with humidity display means insuch a manner as to be visible from outside.

Still another typical example of the inventions disclosed hereinprovides an air-tight package made of a moisture-proofing film, whichcomprises a number of resin-molded semiconductor devices, a plurality ofdevice storing magazines for storing therein a number of resin-moldedsemiconductor devices aligned in a line, an interior box for storingtherein a plurality of magazines while being aligned and in closecontact with one another, a packaging bag for storing therein theinterior box, made of a moisture-proofing sheet and sealed air-tight,and humidity display means disposed inside the packaging bag in such amanner as to be visible from outside.

Still another typical example of the inventions disclosed hereinprovides an air-tight package for a number of surface package typeresin-molded semiconductor integrated circuit devices, which comprisesan exterior box made of cardboard, a number (at least five to six) ofpackaging bags made of a moisture-proofing film, sealed air-tight andstored in the exterior box, a plurality of interior boxes made of paperand stored in the packaging bag, a plurality of tube-like magazines forconveying semiconductor devices, stored in the interior boxes,respectively, a number of surface mount package type resin-moldedsemiconductor integrated circuit devices stored in a plurality ofmagazines, respectively, and humidity display means for displaying aninternal humidity of said packaging bag, disposed inside the packagingbag in such a manner as to be visible from outside the packaging bag.

Still another typical example of the inventions disclosed hereinprovides an air-tight package for a number of surface package typeresin-molded semiconductor integrated circuit devices which comprises anexterior box, a plurality of packaging bags made of a moisture-proofingbag and stored in the exterior box, at least one conveying auxiliarymember for protecting a number (five to six) of resin-moldedsemiconductor devices stored in the packaging bag, a number ofresin-molded semiconductor integrated circuit devices stored in or onthe auxiliary member, and humidity display means for displaying theinternal humidity of the packaging bag, disposed in the packaging bag insuch a manner as to be visible from outside.

Still another typical example of the inventions disclosed herein providean air-tight package for at least one resin-molded semiconductor device,which comprises a packaging bag made of a moisture-proofing film andsealed air-tight, at least one conveying auxiliary member stored in thepackaging bag, at least one resin-molded semiconductor device stored inthe packaging bag and stored in or on the auxiliary member, and humiditydisplay means disposed in the packaging bag in such a manner as to bevisible from outside.

Still another typical example of the inventions disclosed hereinprovides an air-tight package for at least one resin-moldedsemiconductor device, which comprises a packaging bag made of amoisture-proofing bag and sealed air-tight, at least one resin-moldedsemiconductor device stored in the packaging bag, and humidity displaymeans disposed in the packaging bag in such a manner as to be visiblefrom outside.

Still another typical example of the inventions disclosed hereinprovides an air-tight package for at least one resin-moldedsemiconductor device, which comprises a packaging bag made of amoisture-proofing film and sealed air-tight, at least one resin-moldedsemiconductor device stored in the packaging bag, and a drying memberstored or formed inside the packaging bag in such a manner as to bevisible from outside.

Still another typical example of the inventions disclosed hereinprovides an air-tight package for a number of resin-molded semiconductordevices, which comprises a carrier tape made of a firstmoisture-proofing resin sheet and having device storing recesses, aplurality of resin-molded semiconductor devices stored in the recesses,and a second moisture-proofing resin sheet covering the upper surface ofthe recesses and sealed in such a manner as to keep the inside of therecesses air-tight.

Still another typical example of the inventions disclosed hereinprovides a packaging method of resin-molded semiconductor devices, whichcomprises the steps of preserving the resin-molded devices in amoisture-proofing bag lest they should absorb moisture, taking out theresin-molded devices from the moisture-proofing bag, and placing theresin-molded devices on a wiring substrate and soldering the leads ofthe resin-molded devices to the wirings on the wiring substrate undersuch a condition where the resin-molded portion receives thermal impact.

Still another typical example of the inventions disclosed hereinprovides a method of shipping a large number of resin-moldedsemiconductor devices by an air plane, which comprises sealing air-tightthe resin-molded semiconductor devices together with a desiccant in amoisture-proofing bag.

Still another typical example of the inventions disclosed hereinprovides a method of fabricating resin-molded semiconductor devices,which comprises the steps of sealing a semiconductor chip and innerleads by a resin, putting an ink mark to the resulting resin-moldedmember, exposing the resin-molded member as a whole after marking to ahigh temperature for baking the ink, and sealing airtight the devicesafter completion before they absorb moisture.

Still another typical example of the inventions disclosed hereinprovides a method of fabricating a semiconductor memory device, whichcomprises the steps of fixing lead to semiconductor chip holdingportions made of the same metal sheet as that of the leads through oneof the main planes of the tip, bonding pads on the other main plane ofthe chip to inner leads by a bonding wire, coating an organic resincausing less occurrence of α-rays on at least a region of the other mainplane of the chip, where memory cells are formed, forming a resin-moldedmember from which a plurality of leads projects, by molding the chip,the wires, the chip holding members and the inner leads by a resin, andpackaging the resin-molded member by a moisture-proofing bag lest theresin-molded member absorbs the moisture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a package in accordance with the firstembodiment of the present invention;

FIG. 2 is a perspective view of an interior box in the first embodimentdescribed above;

FIG. 3 is a perspective view showing an example of a magazine;

FIG. 4 is an explanatory sectional view of the end portion of themagazine;

FIG. 5 is an explanatory view of an example of a bag;

FIG. 6 is a perspective view showing the appearance and construction ofa transparent moisture-proofing packaging bag in accordance with thesecond embodiment of the present invention;

FIG. 7 is an enlarged sectional view taken along line II—II of FIG. 6and shows the fitting portion of a humidity indicator fitted to theinner side surface of a transparent bag-like moisture-proofing member;

FIG. 8 is a partially cut-away perspective view showing the structure ofthe transparent bag-like moisture-proofing member of themoisture-proofing bag shown in FIG. 6;

FIG. 9 is a perspective view showing the appearance and construction ofa transparent moisture-proofing packaging bag in accordance with thethird embodiment of the present invention;

FIG. 10 is an enlarged sectional view taken along line II—II of FIG. 9and is an enlarged sectional view of a humidity indicator fitted to theinner side surface of a transparent bag-like moisture-proofing member;

FIG. 11 is a partially cut-away perspective view showing the structureof an opaque bag-like moisture-proofing member of the moisture-proofingpackaging bag shown in FIG. 9;

FIGS. 12 to 17 are sectional views showing the appearance ofresin-molded semiconductor devices to which the first to thirdembodiments of the present invention are applied;

FIGS. 18 to 20 show examples of conveying auxiliary members used in thefirst to third embodiments of the present invention, respectively;

FIGS. 21, 21A and 21B show examples of conveying auxiliary members usedin embodiments of the present invention, with FIGS. 21A and 21B beingviews along line 21A—21A and line 21B—21B, respectively, in FIG. 21;

FIG. 22 is an explanatory view showing in detail the packaging method inthe first to third embodiments of the present invention;

FIG. 23 is a sectional view of a memory IC device dealt with in thefirst to third embodiments of the present invention;

FIG. 24 is a schematic view showing the completed state of surfacepackaging in the first to third embodiments of the present invention;and

FIGS. 25( a), 25(b) and 25(c) are schematic views of a solder dippingmethod of a similar package.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described more definitelywith reference to some preferred embodiments thereof shown in theaccompanying drawings.

[Embodiment 1]

A magazine 2 is stored in an interior box 1 made of paper, as shown inFIG. 2. An example of the magazine is shown in FIG. 3. A surface mountpackage type semiconductor package 3 is packaged into the magazine 2 anda stopper 4 is fitted to the end portion of the magazine 2 in order toprevent projection of the package 3 from the magazine 2.

A plurality of packages 3 are packaged into the magazine 2.

Silica gel 5 is put between the wall of the interior box 1 and the sidesurfaces of the magazine 2 as shown in FIG. 2. Preferably, the silicagel 5 is put into the end portions of the magazine for absorbingmoisture. A flange 7 of a lid 6 is folded inward and the lid 6 isclosed. When the package 3 is taken out by lifting up the lid 6, the endopen side of the lid 6 is first affected by external moisture. For thisreason, it is advisable to place the silica gel on the open side of thelid.

The interior box 1 is put into a bag 8 such as shown in FIG. 5 and afterdeaeration, the open portion 9 of the bag 8 is heat-sealed.

The bag 8 is made of a transparent, electrically conductive bag using apolyester having moisture permeability of up to 2.0 g/m²·24 hrs as thebase.

If the bag 8 is transparent, it is very convenient for the management ofthe products because the kind of products, quantity, production lotnumber, and so forth, are put usually on the surface of the interior box1.

An example of the resin films constituting the conductive bag 8 is alaminate film prepared by laminating a polyethylene containing anantistatic agent kneaded therein, a polyester film, a carbon conductivelayer and an acrylic resin protective film in order named from theinside, and further coating a vinylidene chloride film on the laminate.To prevent charge of IC(s) inside the package 8, the surface intrinsicresistance of the conductive bag 8 is up to 10⁶ ohms on the outersurface and up to 10¹¹ ohms on the inner surface.

Cautions to the effect that the devices should be used rapidly afteropening the bag and the bag should be kept in the environment of lowhumidity are printed on the surface of the conductive bag 8 or a label10 bearing such cautions is bonded to the conductive bag 8.

In accordance with the present invention, the surface mount package typepackage 3 is kept in the moisture-proofing bag 8 and is sealedcompletely by deaeration and heat seal 9. Since the silica gel 5 absorbsthe moisture on the opening side and the package 3 is not affected bythe external moisture, a troublesome baking operation becomesunnecessary and even after solder reflow, peel of interface and crack ofthe package can be prevented.

Other desiccants can be used in the embodiment described above in placeof silica gel.

[Embodiment 2]

A second embodiment of the present invention will be explaineddefinitely with reference to the drawings.

In FIGS. 6 to 8 useful for explaining this embodiment, like referencenumerals are used to identify like constituents and repetition ofexplanation of their function will be omitted.

FIG. 6 is a perspective view showing the appearance and structure of atransparent moisture-proofing packaging bag of this embodiment.

As shown in FIG. 6, the transparent moisture-proofing packaging bag ofthis embodiment is made of a transparent bag-like moisture-proofingmember 11. A plurality of electronic components 12 such as surface mountpackage type semiconductor devices are stored in a container 13 and thecontainers 13 are stored in an interior box 14. Furthermore, theinterior box 14 is stored in the bag-like moisture-proofing member 11,and both of its end portions 11A, 11B are sealed. When moisture-proofingpackaging is made, a humidity indicator 15 for detecting the humidityinside the moisture-proofing packaging bag 17 is disposed on the innerside surface of the transparent bag-like moisture-proofing member 11 ata position where the indicator 15 can be seen from outside.

Examples of this humidity indicator 15 are as follows.

-   1. A caution is printed on the inner side surface of the transparent    bag-like moisture-proofing member 11 by an ink containing a material    which changes the color by moisture, such as cobalt chloride, which    serves as the humidity indicator 15. For example, the caution reads    as “When the color of this caution changes from blue to thin violet,    take out surface package type semiconductor devices from the bag and    bake them at 125° C. for 24 hours”.-   2. As shown in FIGS. 6 and 7, the humidity indicator (humidity    detection label) 15 is bonded to the inner side of the transparent    bag-like moisture-proofing member 11 by an adhesive 16 having vent    holes 16A so that it can be confirmed from outside. This humidity    detection label is prepared, for example, by letting paper made of a    pulp absorb a material which changes color by humidity, such as    cobalt chloride.-   3. As shown in FIG. 6, the humidity indicator (humidity detection    label) 15 is bonded to the interior box 14 inside the    moisture-proofing packaging bag 17 or the caution is printed there    by the material which changes color by moisture such as cobalt    chloride.

Incidentally, when the humidity indicator (humidity detection label) 15is bonded in the items 2 and 3 described above, there is no need toprint the caution by the material which changes the color such as cobaltchloride.

Next, the structure of the transparent bag-like moisture-proofing member11 comprises a laminate sheet as shown in FIG. 8.

In FIG. 8, reference numeral 18 represents a polyethylene layer intowhich an antistatic agent is kneaded. This is the innermost layer of themoisture-proofing packaging bag 17. The polyethylene layer 18 containingthe antistatic agent is 63 μm-thick, for example, and has the functionsof preventing frictional charge, heat sealability, openability, and soforth. A polyester film layer 19 having a pin-hole proofing function isdisposed on the polyethylene layer 18 containing the antistatic agent. Apolyester film layer 20 having a barrier layer for preventing intrusionof moisture is disposed on the polyester film layer 19. The barrierlayer 20 is prepared, for example, by coating a vinylidene chloride filmon a 14 μm-thick polyester film. A polyester film layer 21 (which is 12μm thick) is disposed on the barrier layer 20 prepared by coatingvinylidene chloride on the polyester film (14 μm thick), and a 1 μmthick, for example, carbon conductive layer 22 is disposed on thepolyester film 21. The polyester film 21 has the function of reinforcingmechanical strength and dielectric resistance while the carbonconductive layer 22 has the function of preventing charge. The carbonconductive layer 22 is devoid of degradation with time and does not havehumidity dependence. The material of the protective layer 23 hasproperties such that it protects the carbon conductive layer 22,prevents the occurrence of carbon flake dust and has high abrasionresistance and printability.

Next, the method of using the humidity indicator 15 in themoisture-proofing packaging bag 17 will be explained briefly.

First of all, the bag-like moisture-proofing member 11 which is equippedwith the humidity indicator 15 for detecting the internal humidity ofthe moisture-proofing package 17 on the inner side surface of thetransparent bag-like moisture-proofing member 11 at a position where theindicator is visible from outside is prepared, as shown in FIG. 7.

A plurality of containers 13 storing therein a plurality of electroniccomponents 12 such as surface package type semiconductor devices are putinto the interior box 14, the interior box 14 is then put into thebag-like moisture-proofing member 11 and its both end portions 11A and11B are sealed for moisture-proofing packaging.

If the color of the humidity indicator 15 or the caution changes fromblue to thin violet at the time of use of the electronic components 12such as the surface mount package type semiconductor devices, theelectronic components 12 are taken out from the moisture-proofingpackaging bag 17, are then baked at 125° C. for 24 hours and packagingis then made by solder reflow, infrared lamp or vapor phase reflow.

As can be understood from the description given above, since thisembodiment disposes the humidity indicator 15 for detecting the internalhumidity of the transparent moisture-proofing bag 17 at the positionwhere it is visible from outside, the state of hygroscopicity inside thebag 17 can be confirmed from outside the bag. Accordingly, management ofthe moisture-proofing bags 17 can be made easily.

This embodiment can be applied to packaging of all those electroniccomponents other than the surface mount package type semiconductordevices described above which are affected by humidity.

[Embodiment 3]

The third embodiment of the present invention and a semiconductorprocess which is common to the foregoing two embodiments will beexplained with reference to the drawings.

Hereinafter, the description will be made primarily on DRAM by way ofexample.

(1) Fabrication Process in General:

The structure and processes of the semiconductor chip (DRAM, logic IC)as the essence of the semiconductor devices (integrated circuit devices,electronic devices) dealt with in the present invention are described inU.S. Pat. No. 4,612,565 (U.S. Ser. No. 783,531, filed Oct. 3, 1985) andU.S. Pat. No. 4,625,227 (U.S. Ser. No. 744,151, filed Jun. 13, 1985),Therefore, the description will be made by referring partly to thesereferences.

After a wafer step is complete, a wafer is split into each chip bydicing using a rotary blade. The fabrication steps before and after thewafer steps are described in “Electric Integrated Circuits”, JohnAllison, 1975, by McGraw Hill Book Company, pp. 5–10, particularly inFIG. 1.3 (p. 7). As to the dicing technique, refer to U.S. Pat. No.4,016,855 (U.S. Ser. No. 608,733, filed Aug. 28, 1975).

Thereafter, each chip is die-bonded to a lead frame. For detail ofdie-bonding of various kinds of chips, refer to U.S. patent applicationSer. No. 256,110 (filed Apr. 21, 1981), U.S. patent application Ser. No.874,121 (filed Jun. 13, 1986), U.S. patent application Ser. No. 845,332(filed Mar. 21, 1986), U.S. patent application Ser. No. 843,611 (filedMar. 25, 1986), U.S. patent application Ser. No. 898,534 (filed Aug. 21,1986), U.S. patent application Ser. No. 740,420 (filed Jun. 3, 1985),U.S. patent application Ser. No. 758,030 (filed Jul. 23, 1985) and U.S.patent application Ser. No. 767,598 (filed Aug. 20, 1985).

Next, each bonding pad of each pellet and the inner lead terminal of thelead frame are bonded by a bonding wires (about 30 μm thick) of Cu, Al,Au, or the like. Besides the various U.S. patents and patentapplications described above, refer also for the detail of this bondingtechnique to U.S. Pat. No. 4,564,734 (U.S. Ser. No. 476,268, filed Mar.17, 1983), U.S. Pat. No. 4,301,464 (U.S. Ser. No. 55,070, filed Jul. 5,1979), U.S. patent application Ser. No. 898,535 (filed Aug. 21, 1986),and U.S. patent application Ser. No. 723,645 (filed Apr. 16, 1985).

Furthermore, an about 20 to 200 μm-thick high purity polyimide layer orsilicon resin layer is formed by potting on the chip after completion ofbonding in order to prevent any soft errors by α-rays. For the detail ofresin coating, refer to U.S. patent application Ser. No. 256,110. Resincoating for preventing the α-ray soft error may be carried out duringthe wafer process. At this time, a suitable thickness is from about 10μm to about 80 μm and the resin coating is formed by the combination ofspin coating with photolithography in such a manner as to cover at leastthe memory cell mat.

After wire bonding is complete, the lead frame is molded into an epoxyresin material by transfer mold. As to the molding technique, refer tovarious U.S. patents and patent applications described above as well asto “VLSI Technology”, S. M. Sze, 1983, by McGraw-Hill Book Company, pp.574–581.

After molding is complete, the lead frame is withdrawn from the moldingdie and after any fins on the lead are completely removed, theunnecessary portions of the lead frame are cut off, the molded member iscut away from the frame and the leads are shaped in a desired shape.

After these steps, the products are selected and marking is applied tothe approved products. This marking step may be made before cutting theleads. In other words, Sn or the like is plated to the surface of theexposed lead frame after resin molding by electroplating. Thereafter,the resin molded member and the exposed surface of the lead frame arecleansed (washed with water) to remove the plating solution attaching tothem, and after they are dried, they are put to an automatic markingmachine for applying the mark.

In this marking, marks representing the kind of products, class, and thelike, are simultaneously put to the resin-molded member such as MOSsemiconductor devices by offset marking using a rotary drum (transferdrum) or relief direct mark while the lead frame to which a plurality ofsemiconductor devices are fixed is moved in a predetermined direction.At this time, static electricity develops between the transfer drum orthe relief and the resin molded member, but since the frame is kept as awhole at the same potential, the static electricity does not affect theinterior of the semiconductor pellet but is grounded. Thereafter, theprinted marks are baked or dried by a ultraviolet or infrared dryer ormere heat-treatment and adhered tightly to the resin molded member.

Thereafter, each semiconductor device is separated by punching, cuttingand bending and each lead of each MOS semiconductor device or the likebecomes simultaneously an independent lead. The leads are bent in theL-shape on the same side and a dual-in type MOS semiconductor device orthe like free from dielectric breakdown is thus completed.

As described above, baking (mark baking) is made at 150° C. for 3 to 5hours in the case of marking by the ink. If laser marking is employed,on the other hand, baking for drying the ink is not particularlyrequired. For the detail of laser marking, refer to U.S. patentapplication Ser. No. 720,884 (filed Apr. 8, 1985).

After baking is complete, the resin molded electronic devices (such asintegrated circuit devices, semiconductor devices) are put into themoisture-proofing bag shown in the foregoing two embodiments, eitherdirectly or through a suitable auxiliary member (magazine, tray, tape,reel, etc.), within a few days and preferably, within a few hours aftercompletion, together with a desiccant such as silica gel, and are thensealed air-tight.

Thereafter, the resin molded devices are packed into a shipmentcardboard box or the like for shipment while being sealed in the bag.

These semiconductor devices are taken out from the moisture-proofing bagimmediately before mounting. In an ordinary environment, they are takenout within two to three days or within a few hours, before use. Theinventors of this invention found out that if they are exposed to theexternal air for more than one week, they absorb substantiallycompletely the moisture in the external air. Various solder reflowprocesses are used for mounting the semiconductor devices.

(2) Detail of Moisture-Proofing Bag and its Film:

FIG. 9 is a perspective view showing the appearance and structure of anopaque moisture-proofing bag of this embodiment.

As shown in FIG. 9, the opaque moisture-proofing packaging bag of thisembodiment is made of an opaque bag-like moisture-proofing member 11. Aplurality of electronic components 12 such as surface mount package typesemiconductor devices are put into a container 13 and the containers 13are then stored in the interior box 14. After this interior box 14 isput into the bag-like moisture-proofing member 31, its both end portions32A and 32B are sealed for moisture-proofing. When moisture-proofingpackaging is made, the humidity indicator 15 for detecting the internalhumidity of the moisture-proofing bag 31 is disposed on the inner sidesurface of the opaque bag-like moisture-proofing member 31 at a positionwhere it is visible from outside.

Next, an example of this humidity indicator 15 will be given.

Cautions are printed on the inner side surface of the transparentbag-like moisture-proofing member 31 by an ink containing a materialwhich changes the color by humidity, such as cobalt chloride. Thecautions read, for example, as “If the color of the cautions change fromblue to thin violet, take out the surface mount package typesemiconductor devices from the moisture-proofing bag and bake then at125° for 24 hours”.

As shown in FIGS. 9 and 10, the peripheral portion of the humidityindicator (humidity detection label) 15 is bonded directly to the insideof a transparent window 33 disposed at a part of the opaquemoisture-proofing member 31 by an adhesive so that the indicator can beconfirmed from outside. This humidity detection label is prepared, forexample, by letting paper made of a pulp absorb a material which changesthe color by humidity, such as cobalt chloride. For example, it ispossible to let the portion of the surface of the interior boxcorresponding to the window 33 absorb such a material.

As shown in FIGS. 9 and 10, the humidity indicator (humidity detectionlabel) 15 is printed on the interior box 14 of the moisture-proofingpackaging bag 31 or the caution is printed there by the material whichchanges the color by humidity such as cobalt chloride.

When the humidity indicator (humidity detection label) 15 is bonded,there is no need to print the caution by the material changing the colorby humidity, such as cobalt chloride.

Next, the moisture-proofing member 34 at the transparent window portionof the moisture-proofing packaging bag comprises a laminate sheet asshown in FIG. 8.

On the other hand, the portions of the moisture-proofing bag other thanthe transparent window 33 shown in FIG. 10 is made of an opaque sheethaving an aluminum film 35 as shown in FIG. 11.

In FIG. 11, reference numeral 36 represents a polyethylene layer intowhich an antistatic agent is kneaded and which serves as the innermostlayer of the moisture-proofing packaging bag 31. The polyethylene layer36 containing the antistatic agent is 60 μm thick, for example, and hasthe functions of preventing frictional charge, heat sealability,openability, and the like.

An aluminum foil 35 having high moisture-proofness is spread on thispolyethylene layer 36. Since aluminum is a metal, its vapor permeabilityis extremely lower than that of organic films and can effectivelyprevent its intrusion. This aluminum is about 10 μm thick, for example.Furthermore, an about 20 μm-thick polyethylene film layer 39 having highheat moldability is disposed on this aluminum. A polyester film layer(which is 12 μm thick) 38 having high mechanical strength and highwithstand voltage is disposed on the polyethylene film and a 1 μm-thickcarbon conductive layer 37 is disposed on the polyester film layer.Furthermore, an acrylic type protective layer 40 is disposed on thecarbon conductive layer 37. The polyester film layer 38 has the functionof reinforcing mechanical strength and dielectric resistance while thecarbon conductive layer 37 is devoid of degradation with time and doesnot have humidity dependence. The material of the protective layer 40has properties such that it protects the carbon conductive layer 37,prevents the carbon flake dust and has high abrasion resistance and highprintability.

Next, the method of using the humidity indicator 15 in themoisture-proofing packaging bag 31 of this embodiment will be explainedbriefly.

First of all, the bag-like moisture-proofing member 31 which is equippedwith the humidity indicator 15 disposed at the position of thetransparent window 33, where the indicator is visible from outside, onthe inner side surface of the moisture-proofing member 11 is prepared. Aplurality of electronic components 12 such as the surface mount packagetype semiconductor devices are stored in the container 13, thecontainers 13 are then stored in the interior box 14 and after theinterior box 14 is put into the bag-like moisture-proofing member 11,its both end portions 32A and 32B are sealed for moisture-proofing.

When the color of the humidity indicator 15 or the caution changes fromblue to thin violet when using the electronic components 12 such as thesurface mount package type semiconductor devices, the electroniccomponents 12 are taken out from the moisture-proofing bag 31 and bakedat 125° C. for 24 hours. Thereafter, they are mounted by solder reflow,infrared lamp or vapor phase reflow.

As can be understood from the description given above, this embodimentdisposes the humidity indicator 15 for detecting the internal humidityof the opaque moisture-proofing bag 31 at the position where it isvisible from outside. Accordingly, the internal state of hygroscopicityof the bag 31 can be confirmed from outside and its management can bemade easily. Since the moisture-proofing bag 31 is not broken,re-packaging is not necessary after confirmation.

This embodiment can be changed or modified in various manners.

For example, the embodiment can be applied to all those electroniccomponents other than the surface mount package type semiconductordevices described above which are affected by the influence of humidity.

(3) Detail of Resin Molded Electronic Devices as Object of Application:

FIG. 12 shows a package which is called a “gull wing” and generally a“Small Outline Package (SOP)”.

FIG. 13 shows a surface mount package type package which is called a“flat plastic package (FPP) or a squad flat package (QFP)”. Furthermore,FIG. 14 shows a package for use specially for a memory or the like,which is called a “small outline J-bend package (SOJ)”. FIG. 15 shows apackage which is called a “plastic leaded chip carrier (PLCC)” and isused for high density surface mount package. FIG. 16 shows a packagewhich belongs to a butt lead type and is called a “mini-squad package(MSP)”.

Unlike the packages shown already, the package shown in FIG. 17 is of atype in which leads are fitted into holes of a substrate. Therefore, itbelongs to an insert type and is generally called a “dual in-linepackage (DIP)”.

In FIGS. 12 to 17 described above, the semiconductor chip 42 is fixed toa holder such as tabs or islands made of a thin metal sheet through anAg paste 43. The bonding pads on the chip and the inner leads having theAg spot plating layer 44 formed thereon are subjected to ball and wedgebonding by capillary by an Au wire 45 (30 μm diameter), or the like. Theleads 46 are formed by punching out from a 42-alloy or a copper alloyfilm. They are transfer-molded by an epoxy resin 41.

(4) Detail of Conveying Auxiliary Member:

A large number of resin molded devices are stored in various conveyingauxiliary member and are then sealed air-tight depending upon theirapplications.

The auxiliary member will now be explained.

FIG. 18 shows the state of a magazine 54 and the resin molded devices(transistors, ICs, LSIs, etc.) stored in the magazine 54. MSP type resinmolded devices 53 are stacked vertically inside the magazine 54 and apolyethylene sub-stopper 52 and a main stopper made of hard nitrilerubber are packed into the end portion of the magazine. The magazinemain body is made of hard polystylol containing carbon or electricallyconductive soft vinyl chloride.

FIG. 19 shows a tray 55 as one of the auxiliary members. The tray ismade of vinyl chloride to which antistatic treatment is applied, and theresin molded devices 53 are put into square recesses 56 that are alignedin the form of array. In this case, it is possible to put directlysilica gel or the like into each recess 56 and to seal the upper surfaceair-tight by the moisture-proofing sheet. Generally, after the trays arestacked, they are put into the interior box made of paper and thensealed into the moisture-proofing bag.

FIG. 20 shows an auxiliary member which is called a “tape and reel”system. The resin molded devices 53 are held in a line on a carrier tape57 wound on a reel 59 through an adhesive tape 58. After the carriertape 57 is wound on the reel 59, the reel is sealed air-tight one by onein the moisture-proofing bag.

FIGS. 21A, 21B and 210 show another type of the tape and reel system. Inthis case, the resin molded devices 53 are stored in the square recesses56 formed in a line on the carrier type 57 and their upper surface isheat-sealed by a cover tape 60. The tape is wound on the reel under thisstate and the reel is sealed moisture-tight in the same way as above. Inthis case, too, the external moisture-proofing sheet can be eliminatedby changing the cover tape 60 to the moisture-proofing sheet shown inFIGS. 8 and 11 and putting silica gel or the like into each recess 56.

Incidentally, refer to U.S. patent application Ser. No. 879,012 (filedJun. 26, 1986) for the detail of production of magazine and the like.

(5) Detail of Shipment Package of ICs or the Like:

FIG. 22 shows an example of a shipment package of resin molded devices53 (plug-in type or surface mount package type devices). A number ofresin molded devices 53 are stored in a line inside the tube-likemagazine 2 and secured fixedly by a stopper pin 64 and a stopper filler4. A predetermined number of magazines are stored in the interior box 1having low hygroscopicity, made of paper or sheet and stored inside thebag made of the moisture-proofing sheet such as shown in FIG. 8 or 11.The internal pressure of the bag becomes somewhat lower than that of theexternal air and deaeration is made so that the moisture-proofing bagcomes substantially into close contact with the outer surface of theinterior box and air-tight sealing is then made by pressurization or byheating. In this manner, the interior boxes can be stored easily in theexterior box and the storage space becomes small.

On the other hand, the existence of any pin-holes can be discriminatedeasily by putting dry N₂, which may be somewhat pressurized, into thebag in order to secure a gap between the moisture-proofing sheet and theinterior box.

Though the description given above primarily deals with the magazine byway of example, packaging can be made substantially in the same way asabove in the case of the tray and the tape and reel. In addition, eitherone or a plurality of the resin molded ICs may be put directly into themoisture-proofing bag.

It is also possible to put and seal the auxiliary member directly intothe moisture-proofing bag without using the interior box.

Though the desiccant is put into a paper bag or the like and then placedinside the interior box, it may be placed at a suitable air-tightposition such as the recess of the magazine or the carrier tape. Forinstance, the desiccant may be coated and diffused on the inner surfaceof the moisture-proofing sheet.

As described above, a predetermined number of moisture-proofing bagsthat have been sealed air-tight are stored in the exterior box 61 madeof the cardboard and sealed by the adhesive tape 62. After the box isbound by bands 63, the box is shipped.

As to other air-tight sealing methods, particularly the method-whichuses the tray, refer to the afore-mentioned reference Japanese PatentLaid-Open No. 178877/1986.

(6) Detail of Memory Chips and DRAM Devices:

The relationship between the sectional structure of the memory IC deviceand the package in the present invention will be explained. Here, theSOP type package will be described by way of example.

In FIG. 23, a very large number (about 1,000,000) of FETs constitutingDRAM are formed on the upper main plane of the Si substrate 71. On theSi substrate are formed field oxide films forming these devices,insulation films (inorganic films) 72 made of an inter-level PSG(phospho silicate glass), and the like. A number of Al bonding pads 75are disposed further thereon.

On the other hand, the Si substrate 71 is fixed on its lower main planeto the islands or tabs 78 through the Ag paste 77. The size of this chip71 is about 10 mm×5 mm×0.4 mm (high×wide×thick). The lead 80 is made ofthe same 42-alloy as that of the islands, and partial Ag plating 79 isdisposed at the inner lead portion. After ball and wedge bonding is madeto the gap between the inner end of the lead 80 and the bonding pad byan Au wire having a 30 μm diameter, a polyimide resin 73 is formed bypotting onto substantially the entire upper surface of the chip fromabove the former. Thereafter, the structure is transfer-molded by anepoxy resin 76 in a lead frame unit. Solder plating 81 is applied to thelead portions protruding from the mold resin 76.

At this time, the 42-alloy member of the lead and island portion is 0.15mm thick, the mold resin on the upper surface of the package is about 1mm thick, the polyimide film is about 0.1 mm thick, the Ag paste isabout 50 μm thick and the lower surface of the mold resin is about 1 mmthick.

In the package sealed by such a thin resin, if the absorbed moisturecontent is great, evaporation and expansion of the moisture occur firston the lower surface of the tab 78 due to drastic heating at the time ofsoldering and packaging. Subsequently, peel occurs between the resin andthe metal and the package swells. The inventors found out that if theresin cannot withstand the resulting stress at this time, package crackdevelops.

(7) Detail of the Package Mounting Process:

First of all, the outline of the surface mounting process will be given.

Desired wirings are formed on the substrate made of glass-epoxy resin,or the like, by a Cu film or the like, and a solder paste is formed byscreen printing or the like at solder portions (foot print) on thesubstrate. Then, the resin molded devices are mounted onto the solderpaste by a vacuum chuck or like means, and solder in the paste is fusedfor soldering by the solder reflow method such as vapor phase reflow,heating furnace, infrared reflow, and like means.

FIG. 24 shows the state of mounting. In the drawing, reference numeral91 represents the resin molded device of the SOJ type, 92 is the resinmolded device of the SOP type and 93 is the resin molded device of theMSP type. Reference numeral 94 represents the wiring substrate and 95 isthe solder which is reflowed or dipped.

FIGS. 25( a), 25(b) and 25(c) show the solder dipping method. As shownin FIG. 25( a), the resin molded device 93 of the MSP type is fixed insuch a manner that its leads are placed on the screen-printed solderpaste on the substrate 94 by the adhesive 96. Subsequently, it is dippeddownwardly into the solder stream 98 as shown in FIG. 25( b) and is thencooled in such a manner as to attain the state shown in FIG. 25( c).

Though the present invention has thus been described with reference tosome preferred embodiments thereof, it will be obvious to those skilledin the art that the invention is not particularly limited thereto butcan be changed or modified in various manners without departing from thespirit and scope thereof.

1. A packaged device, comprising: a moisture proofing bag; a surfacemount semiconductor device, to be mounted on a printed circuit board,sealed in the moisture proofing bag with dry N₂, the surface mountsemiconductor device being a device which will be subject to heat whenthe surface mount semiconductor device is surface mounted on a printedcircuit board; and a desiccant sealed in said moisture proofing bag. 2.A packaged device according to claim 1, wherein the moisture proofingbag is sealed by heat sealing.
 3. A packaged device according to claim1, wherein the moisture proofing bag is sealed by deaeration and heatsealing.
 4. A packaged device according to claim 1, wherein the moistureproofing bag has a polyethylene layer, and wherein the polyethylenelayer is sealed by heat sealing.
 5. A packaged device according to claim4, wherein the moisture proofing bag has a barrier layer, for preventingintrusion of moisture, outside of the polyethylene layer.
 6. A packageddevice according to claim 1, wherein the moisture proofing bag is madeof a laminate film.
 7. A packaged device according to claim 6, whereinthe laminate film has a barrier layer for preventing intrusion ofmoisture, an inner charge preventing layer formed inside of said barrierlayer and an outer charge preventing layer formed outside of saidbarrier layer.
 8. A packaged device according to claim 1, wherein themoisture proofing bag has a barrier layer for preventing intrusion ofmoisture.
 9. A packaged device according to claim 1, wherein the surfacemount semiconductor device is a surface mount semiconductor devicehaving a surface mount plastic package encapsulating a semiconductordevice.
 10. A packaged device according to claim 1, further comprising amember for storing the surface mount semiconductor device, sealed in themoisture proofing bag.
 11. A packaged device according to claim 10,wherein the member for storing is a magazine.
 12. A packaged deviceaccording to claim 10, wherein the member for storing is a tray.
 13. Apackaged device according to claim 10, wherein the moisture proofing bagis sealed by heat sealing.
 14. A packaged device according to claim 1,wherein the moisture proofing bag has a caution that the device shouldbe prevented from absorbing moisture after opening the bag.
 15. Apackaged device according to claim 14, wherein the caution is printed ona surface of the moisture proofing bag.
 16. A packaged device accordingto claim 14, wherein the caution is bonded on a surface of the moistureproofing bag.
 17. A packaged device according to claim 16, wherein themoisture proofing bag is sealed by heat sealing.
 18. A packaged deviceaccording to claim 16, wherein the moisture proofing bag includes apolyethylene layer, and wherein the polyethylene layer is sealed by heatsealing.
 19. A packaged device according to claim 1, wherein themoisture proofing bag has a caution that the device should be usedrapidly after opening the bag.
 20. A packaged device according to claim1, wherein the moisture proofing bag has a caution that the deviceshould be kept in an environment of low humidity.